Pressure cylinders have long been used to move other mechanical devices such as arms and doors. The piston and piston rod assembly is pneumatically powered and reciprocally strokes between an extended forward position and a retracted return position. One such device is used to open and close sliding doors on the hopper of a coal car for the railroad industry.
When the car door is closed, a yard operator often visually inspects under the coal car door to assure that it is in the fully closed and locked position. While many power cylinders have indicator systems that engage a switch that can actuate an electric signal, the signal indicator may be remote from the cylinder and not visible for easy inspection by the yard operator. Furthermore, known cylinders do not have a secondary internal lock.
What is desired is a power cylinder that can provide an indicator pin at the side wall of the cylinder that extends out to provide a visible indication when the power cylinder is not at the end of a return stroke and retracts when the power cylinder is at the end of the return stroke. What is also needed is a locking pin that mechanically secures the power cylinder at the end of the return stroke.